Unexpected results in React

[Sam]

I need to generate a speciation diagrams for Al+++ ,Ca++,Mg++ ,Fe+++ and Fe++ as a function of pH. To see how speciation diagrams are generated in React I tried the example on pages 214 and 215 of the text: Geochemical and Biogeochemical Reaction Modeling , 2nd edition , by Graig M. Bethke typing in the folowing commands as in the book:

decouple UO2++

10 mmolal Na+

10 mmolal Cl-

1 mmolal UO2++

swap H3PO4 for HPO4--

1 mmolal H3PO4

pH = 2

slide pH = 10

precip = off

go

 

The program ends successfully but when I ask it to plot the results I do not get the diagram which is Figure 14.12 on page page 215 of the text.Instead React gives me a diagram (generated by Gtplot) that has the vertical axis labelled "components in fluid (moles)" and a horizontal axis labeled "Rxn progress" the plotted results are completely differrent ,of course ,from that shown in figure 14.12 in the text. Please help,as I am already behind schedule on generating these speciation diagrams.

[Sam]

I need to generate a speciation diagrams for Al+++ ,Ca++,Mg++ ,Fe+++ and Fe++ as a function of pH. To see how speciation diagrams are generated in React tried the example on pages 214 and 215 of the text: Geochemical and Biogeochemical Reaction Modeling , 2nd edition , by Graig M. Bethke typing in the folowing commands as in the book:

decouple UO2++

10 mmolal Na+

10 mmolal Cl-

1 mmolal UO2++

swap H3PO4 for HPO4--

1 mmolal H3PO4

pH = 2

slide pH = 10

precip = off

go

 

The program ends successfully but when I ask it to plot the results I do not get the diagram which is Figure 14.12 on page page 215 of the text.Instead React gives me a diagram that has on the vertical axis labelled "components in fluid (moles)" and a horizontal axis labeled "Rxn progress" the plotted results are completely differrent ,of course ,from that shown in figure 14.12 in the text. Please help,as I am already behind schedule on generating these speciation diagrams.

[Brian Farrell]

Hi Sam,

 

After you run the simulation in React, you use the interactive program Gtplot to display your results. By default, fluid component concentration and rxn progress appear on the axes, but these can be changed with a few mouse clicks.

 

The fluid component concentration refers to the total concentration in solution that you specify on the Basis pane. Na, for example, is present in this simulation as Na+, NaCl, NaHPO4-, and NaOH species, each of which will add up to 10 mmolal. U and P in solution are much more complicated. Since you're interested in a speciation diagram, you'll need to select the individual species that you are interested in. As a side note, since Cl- is the balancing ion, it is adjusted somewhat from it's specified value of 10 mmolal to maintain electroneutrality.

 

Reaction progress is a vague term and depends on how your reaction path model is set up. It might refer to time in a kinetic simulation, or temperature in a polythermal run. Here it closely mirrors pH, since your reaction path involves incrementally adjusting pH.

 

You should read the "Using Gtplot" section of the GWB Reaction Modeling Guide for details of how to select the appropriate variables for plotting, and how to edit the appearance of your plots.

 

Hope this helps,

 

Brian Farrell

Aqueous Solutions LLC